The present invention relates to a gear-controlled height-adjusting mechanism for armrest of office chair, and more particularly to a gear-controlled height-adjusting mechanism that enables the armrest of an office chair to move upward in multiple stages and to move downward freely to a desired or a lowest position possible.
The currently available office chairs include armrests that are differently designed to show various appearances, and are provided with different adjusting structures for users to conveniently adjust the height and/or the openness of the armrests, so that the office chairs are more comfortable for sitting and have increased value. U.S. Pat. No. 6,336,680 B1 granted to the same applicant discloses a height-adjusting structure for armrest, in which each armrest is allowed to freely move up and down during the height adjustment. It is uneasy for a user to control the adjusting structure and accurately locate the armrests at a selected height, and the armrests tend to unnecessarily slide all the way down to a lowest position.
It is a primary object of the present invention to provide a gear-controlled height-adjusting mechanism for armrest of office chair, with which the armrest of the office chair can be adjusted to a higher position in multiple stages and to a desired lower position freely via a release mechanism.
To achieve the above and other objects, the height-adjusting mechanism of the present invention mainly includes:
an armrest support being generally in the shape of letter T to include a flat top portion for an armrest to mount thereto and a flat long body downward extended from the flat top portion for fixing to one side of an office chair;
a housing being provided at one side of an inner wall surface with a vertical row of equally spaced locating holes, and the armrest support being upward and downward slidably mounted in the housing;
an elongate slide member being movably connected to an upper outer side of the armrest support, such that the slide member can be pulled upward and released to elastically return to an initial lower position, and the slide member including a handle laterally outward extended from a top of the slide member, and a rack downward extended from a lower end of the slide member with teeth of the rack projected toward the armrest support; and
a gear set including a driving gear and a driven gear, which are connected to each other with a pivotal shaft to mount in an opening provided at a middle portion of the armrest support, the driving gear meshing with the rack on the slide member, the driven gear including a transmission gear and a locating gear that are integrally formed into one unit, the transmission gear having teeth adapted to engage with the locating holes on the housing; and the gear set also including a unidirectional catch means provided between the driving gear and the driven gear, the unidirectional catch means being adapted to bring the driven gear to rotate forward along with the driving gear when the latter rotates forward, and to idle when the driving gear rotates in a reverse direction.
Whereby when the handle of the slide member is alternately pulled upward and released, the driving gear meshing with the rack is caused by the rack to rotate forward and backward, respectively, and the driven gear is caused by the unidirectional catch means to rotate in one forward direction with teeth of the transmission gear engaging with the locating holes on the housing to gradually move the armrest support upward in multiple stages and guided by the spaced locating holes.
The present invention also includes a release mechanism that includes a vertically extended long slot provided near an upper end of the armrest support, a bar horizontally projected from an upper rear end of the slide member for extending through the long slot, a push member pivotally connected at an end via a pivotal shaft to a rear side of the armrest support to locate above and abut at a lower middle point on the bar extended through the long slot, a return spring mounted between the flat top portion of the armrest support and the push member to normally push the push member to a low position, and a vertically extended link having an upper end connected to another end of the push member opposite to the pivotal shaft and a lower end engaged with a catch pawl member mounted on the armrest support to engage with the locating gear. Whereby when the slide member is pulled to a highest position possible, the rearward extended bar drives the push member to pivotally turn about the pivotal shaft and accordingly lift the link, causing the catch pawl member connected to the lower end of the link to pivotally rotate and disengage from the locating gear, and therefore allowing the locating gear to idle freely and the armrest support to be freely pushed downward.